CN117313293A - Small signal equivalent modeling method, system, terminal and medium for direct-drive wind farm - Google Patents

Abstract

The invention relates to the field of equivalent modeling of wind power plants, and particularly discloses a small-signal equivalent modeling method, a system, a terminal and a medium for a direct-drive wind power plant, wherein the equivalent impedance model of a wind power plant is obtained by performing aggregate approximate calculation on the impedance of the wind power plant; calculating the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine generator to each parameter in the full frequency band, dividing the full frequency band into a plurality of frequency bands, and selecting at least one parameter with the maximum sensitivity in each frequency band as a dominant factor parameter of the current frequency band; identifying dominant factor parameters of the current frequency band for each frequency band to correct errors formed by aggregate approximate calculation; and obtaining a final equivalent impedance model of the wind turbine generator by aggregating the approximate calculated equivalent impedance model of the wind turbine generator and the dominant factor parameter identification result. The equivalent impedance model has better accuracy in both time domain and frequency domain, and can maintain the accuracy of impedance characteristics under the condition of changing the operating point.

Description

A direct drive wind farm small signal equivalent modeling method, system, terminal and medium

Technical field

The invention relates to the field of equivalent modeling of wind farms, and specifically relates to a direct-drive wind farm small signal equivalent modeling method, system, terminal and medium.

Background technique

The detailed impedance model of large-scale wind farms has a high order, and numerical analysis faces the problem of "curse of dimensionality". In order to reduce the order of the impedance model and improve the efficiency of small disturbance stability analysis, the wind farm equivalent method can be used to simplify the process.

At present, wind farm equivalent methods can be mainly divided into capacity weighted average method and parameter identification method. The capacity weighted average method obtains equivalent wind turbine parameters by aggregating the physical parameters of wind turbines within the wind farm. The parameter identification method identifies the equivalent wind turbine parameters based on the actual measured or simulated data of the dynamic response of the wind farm grid connection point.

However, the above equivalent methods are more derived from the research of large signal analysis. The equivalent targets are mostly the correspondence of time domain waveforms before and after the equivalent. They do not pay attention to the consistency of the frequency domain characteristics before and after the equivalent, and are not suitable for small signal analysis. Some studies improve the consistency of the frequency domain characteristics of the equivalent model by comparing frequency domain indicators such as dominant modes and synchronous oscillation frequency bands before and after equivalence. However, this type of method only focuses on the equivalent accuracy within a specific frequency band. The equivalent model cannot reflect the dynamic characteristics of the entire frequency band, and the accuracy of the original equivalent model often decreases after the wind farm operating conditions change, making it unable to meet the analysis requirements.

Contents of the invention

In order to solve the above problems, the present invention provides a direct drive wind farm small signal equivalent modeling method, system, terminal and medium, which combines the aggregation calculation of equivalents with parameter identification and correction, and can quickly obtain the equivalent model, and the model can be used in real time. It has good accuracy in both domain and frequency domain, and can be used in time domain analysis, impedance characteristic analysis, etc.

Firstly, this technical solution provides a small-signal equivalent modeling method for direct-drive wind farms, which includes the following steps:

Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine;

The wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine equivalent impedance model. The wind turbine equivalent impedance model is a function of circuit parameters and control parameters;

Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the dominant factor parameter of the current frequency band;

For each frequency band, the dominant factor parameters of the current frequency band are identified to correct the errors caused by the aggregation approximation calculation;

By aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, the final wind turbine equivalent impedance model is obtained.

In an optional implementation, the wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain a wind turbine equivalent impedance model, which specifically includes:

(a) Ignore the influence of the collector line, treat multiple wind turbines in the same branch as a purely parallel relationship, and consider that the operating points, circuit parameters and control parameters of the wind turbines in the same branch are the same, and the impedance of each wind turbine is the same , assuming that there are N wind turbines directly connected in parallel on the branch, the aggregate impedance of the wind turbines is expressed as:

(1)

Among them, Z _g is the filter impedance, Z _gsc is the grid side converter impedance, Z _ig and Z _ug are the phase locked loop impedances, and E is the unit matrix;

(b) According to the principle of parallel connection, the quantitative relationship between the impedances of each part of the fan unit before and after equal value is obtained. The formula is expressed as:

(2).

In an optional implementation, the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter is calculated in the entire frequency band, the entire frequency band is divided into multiple frequency bands, and at least one with the highest sensitivity in each frequency band is selected. Parameters are the dominant factor parameters of the current frequency band, specifically including:

(a) Define the control parameters and circuit parameter set of the wind turbine, expressed as:

x _{WT_para} ={ x ₁ , x ₂ , _… , x _D } (3)

Among them, D represents the number of parameters;

(b) In the full frequency range [H1, H2] Hertz, the sensitivity is calculated for all parameters every h Hertz step. The sensitivity K _s calculation formula is expressed as:

K _si = (4)

K _si represents the sensitivity of the i-th parameter;

(c) Divide the entire frequency band into M frequency bands, calculate the average sensitivity of each parameter in each frequency band, and select at least one parameter with the largest average sensitivity in each frequency band as the dominant factor parameter of the current frequency band.

In an optional implementation, for each frequency band, the dominant factor parameters of the current frequency band are identified to correct the error caused by the aggregated approximation calculation, specifically including:

For each frequency band, the particle swarm algorithm is used to identify the dominant factor parameters of the current frequency band. The fitness function of the particle swarm algorithm is:

(5)

Among them, Z _br represents the detailed impedance of the equivalent front branch of the wind turbine, and Z _br ^eq represents the equivalent impedance of the branch;

s is the frequency domain operator, s _{m, min} , s _{m, max} represent the boundary point of the m-th frequency band interval, is the j-th dominant factor parameter of the m-th frequency band.

In an optional implementation, the final wind turbine equivalent impedance model is obtained by aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, which specifically includes:

Through formula (1) and formula (5), the final wind turbine equivalent impedance model is obtained, and the expression is:

(7)

Among them, d represents the d-axis component in the dq coordinate system, and q represents the q-axis component in the dq coordinate system.

In an optional implementation, when performing an aggregated approximate calculation on the wind turbine impedance of the expanded wind turbine unit to obtain the wind turbine equivalent impedance model, the following steps are also included:

Perform an aggregate approximate calculation on the collector line impedance of the expanded wind turbine to obtain the collector line equivalent impedance model;

The transformer equivalent impedance model is obtained by aggregate approximate calculation of the transformer impedance of the expanded wind turbine.

In an optional implementation, an aggregate approximate calculation is performed on the collector line impedance of the expanded wind turbine to obtain a collector line equivalent impedance model, which specifically includes:

The constant power loss method is used for equivalence. It is considered that the power loss on the collector line before and after equivalence is inconvenient. The collector line is equivalent to an aggregate impedance. Then the expression of the collector line equivalent impedance model is:

(8)

Among them, Z _Li is the line impedance of the i-th unit branch; P _Li is the loss flowing through the impedance Z _Li ;

Perform an aggregated approximate calculation on the transformer impedance of the expanded wind turbine to obtain the transformer equivalent impedance model, which includes:

If the end transformer of a wind turbine is equivalent to an expansion transformer located at the end of an equivalent wind turbine, and the impedance of the expansion transformer is the parallel connection of the impedances of all wind turbine end transformers, then the calculation formula for the equivalent capacity and equivalent impedance of the expansion transformer is expressed for:

(9)

Among them, S _{T_eq} and Z _{T_eq} are the equivalent capacity and equivalent impedance of the expansion transformer respectively, and S _Ti and Z _Ti are the capacity and impedance of _{the i} -th wind turbine unit end transformer in the original wind farm.

In the second aspect, the technical solution of the present invention provides a direct-driven wind farm small signal equivalent modeling system, including:

Equivalent impedance model aggregation calculation module: Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine; the wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine, etc. Value impedance model, the wind turbine equivalent impedance model is a function of circuit parameters and control parameters;

Dominant factor parameter selection module: Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the current The dominant factor parameters of the frequency band;

Dominant factor parameter identification module: For each frequency band, identify the dominant factor parameters of the current frequency band to correct the error caused by the aggregation approximation calculation;

Equivalent impedance model correction module: By aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, the final wind turbine equivalent impedance model is obtained.

In a third aspect, the technical solution of the present invention provides a terminal, including:

Memory used to store small signal equivalent modeling programs for direct drive wind farms;

A processor, configured to implement the steps of the direct drive wind farm small signal equivalent modeling method described in any one of the above when executing the direct drive wind farm small signal equivalent modeling program.

In the fourth aspect, the technical solution of the present invention provides a computer-readable storage medium. A direct-drive wind farm small signal equivalent modeling program is stored on the readable storage medium. The direct-drive wind farm small signal equivalent modeling program is When the module program is executed by the processor, the steps of the direct drive wind farm small signal equivalent modeling method described in any of the above items are implemented.

The invention provides a direct-drive wind farm small signal equivalent modeling method, system, terminal and medium. Compared with the existing technology, it has the following beneficial effects: first, impedance aggregation approximate calculation is performed based on the impedance series and parallel principle, and secondly, based on actual measurement The impedance data identifies the key parameters in the aggregated impedance calculation model by frequency bands. The error caused by the impedance aggregation approximate calculation is corrected through parameter identification. The equivalent model can be quickly obtained, and the key parameters are identified by frequency bands to make the equivalent impedance model. It has good accuracy in both time domain and frequency domain, and can be used in time domain analysis, impedance characteristic analysis, etc., and can maintain the accuracy of impedance characteristics when the operating point changes, thus being suitable for the stability of wind farm grid connection. Analysis and stable domain evolution.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions of the prior art more clearly, the following will briefly introduce the drawings needed to describe the embodiments or the prior art. Obviously, the drawings in the following description are only For some embodiments of the present invention, those of ordinary skill in the art can also obtain other drawings based on these drawings without exerting creative efforts.

Figure 1 is a schematic diagram of a direct drive wind farm.

Figure 2 is a schematic flow chart of a direct-drive wind farm small signal equivalent modeling method provided by an embodiment of the present invention.

Figure 3 is a schematic impedance diagram of the detailed model, calculation parameter equivalent model and identification parameter equivalent model under the same operating point.

Figure 4 is a schematic diagram of the impedance of the detailed model, calculation parameter equivalent model and identification parameter equivalent model under different operating points.

Figure 5 is a schematic structural block diagram of a direct drive wind farm small signal equivalent modeling system provided by an embodiment of the present invention.

Figure 6 is a schematic structural diagram of a terminal provided in Embodiment 5 of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the invention belongs. The terminology used herein in the description of the invention is for the purpose of describing specific embodiments only and is not intended to limit the invention.

Key terms appearing in the present invention are explained below.

PMSG: Permanent Magnet Synchronous Generator, direct drive permanent magnet synchronous wind turbine unit.

Grid: Grid.

SVG: Static Var Generator, static var generator.

Figure 1 is a schematic diagram of a direct drive wind farm. The elements of the direct drive wind turbine impedance Z _WT are high-order. Wind farms generally contain dozens or hundreds of wind turbines and multiple collector lines, with impedance levels reaching thousands of levels, significantly increasing the computational complexity. In order to facilitate online analysis of the system's small-disturbance stability region, this chapter proposes an equivalent method for wind farm impedance aggregation calculation and key parameter identification. Firstly, based on the principle of series and parallel impedance, an approximate calculation method of impedance aggregation is proposed. Secondly, based on the measured impedance data, an identification method for key parameters of aggregate impedance is proposed. Through parameter identification, the error caused by the approximate calculation of impedance aggregation can be corrected.

Figure 2 is a schematic flow chart of a direct-drive wind farm small signal equivalent modeling method provided by an embodiment of the present invention. Among them, the execution subject in Figure 2 can be a direct-drive wind farm small signal equivalent modeling system. The direct-drive wind farm small signal equivalent modeling method provided by the embodiment of the present invention is executed by computer equipment. Correspondingly, the direct-drive wind farm small signal equivalent modeling system runs in the computer equipment. Depending on different needs, the order of steps in this flowchart can be changed, and some can be omitted.

As shown in Figure 2, the method includes the following steps.

S1, using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine.

S2. Perform an aggregated approximate calculation on the wind turbine impedance of the expanded wind turbine to obtain the wind turbine equivalent impedance model. The wind turbine equivalent impedance model is a function of circuit parameters and control parameters.

S3, calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the dominant factor of the current frequency band parameter.

S4. For each frequency band, identify the dominant factor parameters of the current frequency band to correct the error caused by the aggregation approximation calculation.

S5: Obtain the final wind turbine equivalent impedance model by aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results.

According to the wind farm time domain large signal modeling guidelines formulated by the International Electrotechnical Commission (IEC) and the Western Electric Power Coordination Council (WECC), a wind farm composed of wind turbines of the same type can be equivalent to an expanded wind turbine. However, the impedance frequency domain model exhibits strong coupling characteristics in a wide frequency range, and it is difficult for a single equivalent unit to guarantee its accuracy. This paper adopts the principle of multi-machine equivalent modeling, which can take into account both accuracy and computational efficiency. Since the models and electrical parameters of wind turbines on the same branch are usually the same, the wind turbines on each branch can be equivalent to an expanded wind turbine.

The following is a description of the aggregated approximate calculation of the impedance equivalent model in this embodiment. Generally, the calculation of the impedance equivalent model of a wind farm includes model calculations in three aspects: wind turbine impedance, collector line impedance and transformer impedance. Since the impedance of the wind turbine is much greater than the sum of the impedances of the collector line and the transformer, the object of subsequent parameter identification in this embodiment is selected as the impedance of the wind turbine, that is, the dominant factor parameters of the equivalent impedance model of the wind turbine are identified, and the equivalent value of the wind turbine is corrected Error in the calculation of the aggregate approximation of the impedance model.

(1) Aggregation approximate calculation of wind turbine equivalent impedance model

Since the impedance of direct-drive wind turbines is usually much greater than the sum of the impedances of the collector line and the transformer, it can be assumed that N units on the wind farm branch are directly connected in parallel. In a direct drive wind farm, the impedance of the wind turbine is much greater than the impedance of the collector line, so the influence of the collector line can be ignored in the equivalent derivation part, and the wind turbine is considered to be in a pure parallel relationship. At the same time, it is considered that the operating points, circuit parameters and control parameters of wind turbines in the same branch are the same. Therefore, the impedance of each wind turbine is also considered to be the same. The aggregate impedance of the wind turbines in the direct-drive wind farm in this embodiment is approximately expressed as:

(1)

Among them, Z _g is the filter impedance, Z _gsc is the grid side converter impedance, Z _ig and Z _ug are the phase locked loop impedances, and E is the unit matrix.

According to the principle of parallel connection, the quantitative relationship between the impedances of each part of the fan unit before and after equal value is obtained, and the formula is expressed as:

(2)

(2) Aggregation approximate calculation of equivalent impedance module of collector line

The collector lines are equalized using the constant power loss method, that is, the power loss on the collector lines is considered unchanged before and after the equalization, and the wind farm collector network is equivalent to an aggregate impedance. In this embodiment, the equivalent impedance model expression of the collector line is:

(3)

Among them, Z _Li is the line impedance of the i-th unit branch; P _Li is the loss flowing through the impedance Z _Li .

(3) Aggregation approximate calculation of transformer equivalent impedance model

For the machine-side transformer of the wind turbine in the wind farm, it is equivalent to an expansion transformer located at the machine-side of the equivalent wind turbine. The capacity of the expansion transformer is the sum of the capacities of all wind turbine generator-side transformers in the original wind farm. The impedance of the expansion transformer is the parallel connection of the impedances of all wind turbine generator end transformers. In this embodiment, the calculation formula for the equivalent capacity and equivalent impedance of the expansion transformer is expressed as:

(4)

Among them, S _{T_eq} and Z _{T_eq} are the equivalent capacity and equivalent impedance of the expansion transformer respectively, and S _Ti and Z _Ti are the capacity and impedance of _{the i} -th wind turbine unit end transformer in the original wind farm.

There are errors in the impedance aggregation approximate calculation in the previous section. The accuracy of the equivalent impedance of the wind farm branch can be improved by correcting some key parameters. Traditional equivalent parameter identification is mostly aimed at time domain equivalent models under large disturbances. If it is applied to the equivalent value of the small signal model, it is difficult to ensure the accuracy of the equivalent impedance in the entire frequency band. Since the impedance exhibits strong nonlinearity in a wide frequency band, this embodiment proposes a method of modifying the dominant parameters in frequency bands.

First, the parameter sensitivity of broadband impedance is analyzed. Since the impedance of direct-drive wind turbines is usually much greater than the sum of the impedances of the collector line and the transformer, the object of parameter identification is selected as the equivalent wind turbine unit. The approximately calculated impedance Z _br in equation (1) is a function of circuit parameters and control parameters. Some control parameters and electrical parameters of the equivalent model are shown in the table below. Select the dominant factor parameters from these parameters.

Table 1: Partial parameter table of direct drive fan

This embodiment first calculates the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the full frequency band, then divides the full frequency band into multiple frequency bands, and selects at least one parameter with the highest sensitivity in each frequency band as the current The dominant factor parameters of the frequency band.

Define the control parameters and circuit parameter set of the wind turbine, expressed as:

x _{WT_para} ={ x ₁ , x ₂ , _... , x _D } (5)

Among them, D represents the number of parameters

In order to obtain the dominant factor parameters of impedance characteristics, impedance sensitivity analysis is performed. This embodiment calculates the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine generator to each parameter in the full frequency band. The sensitivity K _s calculation formula is expressed as:

K _si = (6)

K _si represents the sensitivity of the i-th parameter.

The sensitivity K _s of formula (6) is a function of the frequency domain operator s. Since the impedance has strong nonlinear characteristics, the sensitivity exhibits nonlinear characteristics in a wide frequency range. In this embodiment, in the wide frequency band [H1, H2] Hertz range, the sensitivity K _s represented by formula (6) is calculated once every h Hertz step for all parameters. For example, in the range of 0-1000 Hz, all parameters are calculated once every 1 Hz step. sensitivity.

After calculating several sensitivities for all parameters, the dominant factor parameters are found based on the sensitivity of each parameter. In this embodiment, the entire frequency band is divided into M frequency bands, and the dominant factor parameters of the current frequency band are found in each frequency band. Specifically, the average value of the sensitivity of each parameter is calculated in each frequency band, and at least one parameter with the largest average sensitivity in each frequency band is selected as the dominant factor parameter of the current frequency band.

After calculation, in each frequency band, the sensitivity of the proportional and integral coefficients of the direct-drive fan current inner loop, the proportional and integral coefficients of the phase-locked loop, and the resistance and inductance of the filter are all higher than those of other parameters. Consider these parameters as the dominant factor parameters.

By deriving the equivalent control parameters and circuit parameters of the wind turbine through the impedance expression of the direct drive wind turbine, the equivalent calculation method of the control parameters of the direct drive wind turbine under the condition of small collector line impedance can be obtained, which is expressed as:

(7)

Among them, k _p and k _i are the proportional and integral coefficients of the direct drive fan current inner loop, k _{p -PLL} and k _{i -PLL} are the proportional and integral coefficients of the phase locked loop, L _g and R _g are the resistance and inductance of the filter. , the subscript eq represents the corresponding parameter after equivalent value.

Finally, the parameters of the dominant factors are modified. Select the impedance of the target branch before equivalence as the equivalence target. By comparing the impedance before and after equivalence, select the dominant factor parameters of each frequency band as the identification object for segmentation identification, and correct and calculate the equivalent part of each frequency band. error.

This embodiment uses particle swarm algorithm to identify small signal equivalent parameters in frequency bands. Particle swarm optimization is an adaptive iterative algorithm based on population global search, which has the advantages of low optimization function requirements and fast convergence speed. The particle swarm algorithm is trained in advance and is trained using measured impedance data. The measured impedance data can be the impedance characteristics of actual direct-drive wind turbines measured using RTLab frequency sweep. RT-LAB is an industrial-grade system real-time simulation platform launched by Canada's Opal-RT Technologies. The frequency scanning method can measure the impedance characteristics of the unit by injecting disturbances at the unit end.

For parameter identification in the m-th partition, the fitness function of the PSO algorithm can be written as:

(8)

Among them, Z _br represents the detailed impedance of the equivalent front branch of the wind turbine, and Z _br ^eq represents the equivalent impedance of the branch.

s is the frequency domain operator, s _{m, min} , s _{m, max} represent the boundary point of the m-th frequency band interval, is the j-th dominant factor parameter of the m-th frequency band, m=1, 2,...,M.

Through the impedance aggregation approximate calculation of formula (1) and the dominant parameter identification of formula (8), the branch equivalent impedance expression can be obtained as:

(9)

Among them, d represents the d-axis component in the dq coordinate system, and q represents the q-axis component in the dq coordinate system.

The dq coordinate system is a mathematical model based on three-phase current or voltage, which can convert a three-phase circuit into a two-phase circuit for analysis and calculation. The dq_coordinate system consists of two mutually perpendicular axes, the d-axis is consistent with the phase of the three-phase voltage or current, and the q-axis is perpendicular to the d-axis. The dq coordinate system can convert three-phase voltage or current into two orthogonal dq-axis components, thereby simplifying the complexity of calculation and analysis, and is often used in vector control.

Eight fans under the same branch were selected to verify the equivalent effect. In order to match the actual operating conditions of the wind farm as much as possible, the calculation example sets the active power generated by the eight wind turbines in the same branch to be different. First, the equivalent model parameters are calculated using the equivalent calculation method, then the sensitivity of the key parameters of the equivalent impedance model is analyzed, and finally the impedance characteristic parameters are identified based on the particle swarm algorithm.

The detailed impedance model, calculation parameter equivalent impedance model and identification parameter equivalent impedance model under the same operating point are shown in Figure 3. As can be seen from Figure 3, the impedance characteristics of the equivalent model formed by calculating equivalent values are quite different from the impedance characteristics of the original branch model, which cannot meet the needs of small interference analysis. Therefore, the particle swarm algorithm needs to be used for parameter identification and correction of calculation equivalent errors. As can be seen from Figure 3, after parameter identification based on particle swarm algorithm, the impedance characteristics of the identified parameter equivalent impedance model are basically consistent with the original branch model, and the equivalent accuracy is greatly improved. Specifically, the error of each impedance is within 0.5%.

In order to verify the accuracy of the equivalent model at different operating points. The detailed impedance model and the identification parameter equivalent impedance model with branch powers of 10 MW, 15 MW and 20 MW were compared. The results are shown in Figure 4. Under different active powers, the impedance values of Zdd and Zqd remain unchanged and are not affected by the power operating point. The amplitudes of Zdq and Zqq increase with the increase of power. It can be concluded that the equivalent model proposed by this method has high accuracy at different operating points. Therefore, the equivalent model can be applied to stability analysis under different working conditions.

The above describes in detail an embodiment of a direct drive wind farm small signal equivalent modeling method. Based on the direct drive wind farm small signal equivalent modeling method described in the above embodiment, embodiments of the present invention also provide a A small-signal equivalent modeling system for direct-drive wind farms corresponding to this method.

Figure 5 is a schematic structural block diagram of a direct-drive wind farm small-signal equivalent modeling system provided by an embodiment of the present invention. The direct-drive wind farm small-signal equivalent modeling system 500 can be divided into multiple systems according to the functions it performs. functional modules, as shown in Figure 5. The functional modules may include: an equivalent impedance model aggregation calculation module 510, a dominant factor parameter selection module 520, a dominant factor parameter identification module 530, and an equivalent impedance model modification module 540. The module referred to in the present invention refers to a series of computer program segments that can be executed by at least one processor and can complete fixed functions, which are stored in the memory.

Equivalent impedance model aggregation calculation module 510: Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine; the wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine Equivalent impedance model, the wind turbine equivalent impedance model is a function of circuit parameters and control parameters.

Dominant factor parameter selection module 520: Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine generator to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as The dominant factor parameters of the current frequency band.

Dominant factor parameter identification module 530: For each frequency band, identify the dominant factor parameters of the current frequency band to correct errors caused by aggregated approximation calculations.

Equivalent impedance model modification module 540: Obtain the final wind turbine equivalent impedance model by aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results.

The small signal equivalent modeling system of the direct drive wind farm in this embodiment is used to implement the aforementioned small signal equivalent modeling method of the direct drive wind farm. Therefore, the specific implementation in the system can be found in the direct drive wind farm small signal in the previous article. The equivalent modeling method is an embodiment part. Therefore, its specific implementation can be referred to the description of the corresponding embodiments, and will not be introduced here.

In addition, since the small signal equivalent modeling system of the direct drive wind farm in this embodiment is used to implement the aforementioned small signal equivalent modeling method of the direct drive wind farm, its function corresponds to the function of the above method, and will not be described again here. .

FIG. 6 is a schematic structural diagram of a terminal 600 provided by an embodiment of the present invention, including a processor 610, a memory 620 and a communication unit 630. The processor 610 implements the following steps when used to implement the direct drive wind farm small signal equivalent modeling program stored in the memory 620:

Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine;

The wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine equivalent impedance model. The wind turbine equivalent impedance model is a function of circuit parameters and control parameters;

Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the dominant factor parameter of the current frequency band;

For each frequency band, the dominant factor parameters of the current frequency band are identified to correct the errors caused by the aggregation approximation calculation;

By aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, the final wind turbine equivalent impedance model is obtained.

The terminal 600 includes a processor 610, a memory 620 and a communication unit 630. These components communicate through one or more buses. Those skilled in the art can understand that the structure of the server shown in the figure does not limit the invention. It can be a bus structure, a star structure, or More or fewer components may be included than shown, or certain components may be combined, or may be arranged differently.

Among them, the memory 620 can be used to store execution instructions of the processor 610. The memory 620 can be implemented by any type of volatile or non-volatile storage terminals or their combination, such as static random access memory (SRAM), electronic Erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic or optical disk . When the execution instructions in the memory 620 are executed by the processor 610, the terminal 600 is enabled to perform some or all of the steps in the following method embodiments.

The processor 610 is the control center of the storage terminal, using various interfaces and lines to connect various parts of the entire electronic terminal, by running or executing software programs and/or modules stored in the memory 620, and calling data stored in the memory, To perform various functions of the electronic terminal and/or process data. The processor may be composed of an integrated circuit (IC for short), for example, it may be composed of a single packaged IC, or it may be composed of multiple packaged ICs connected with the same function or different functions. For example, the processor 610 may only include a central processing unit (Central Processing Unit, CPU for short). In the embodiment of the present invention, the CPU may be a single computing core or may include multiple computing cores.

The communication unit 630 is used to establish a communication channel so that the storage terminal can communicate with other terminals. Receive user data sent by other terminals or send user data to other terminals.

The invention also provides a computer storage medium. The storage medium here can be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (English: random access memory). , abbreviation: RAM), etc.

The computer storage medium stores a direct drive wind farm small signal equivalent modeling program. When the direct drive wind farm small signal equivalent modeling program is executed by the processor, the following steps are implemented:

Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine;

The wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine equivalent impedance model. The wind turbine equivalent impedance model is a function of circuit parameters and control parameters;

Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the dominant factor parameter of the current frequency band;

For each frequency band, the dominant factor parameters of the current frequency band are identified to correct the errors caused by the aggregation approximation calculation;

By aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, the final wind turbine equivalent impedance model is obtained.

Those skilled in the art can clearly understand that the technology in the embodiments of the present invention can be implemented by means of software plus the necessary general hardware platform. Based on this understanding, the technical solutions in the embodiments of the present invention can be embodied in the form of software products in essence or in part that contribute to the existing technology. The computer software products are stored in a storage medium such as a USB flash drive or mobile phone. Hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program code, including a number of instructions to make a computer terminal (It can be a personal computer, a server, or a second terminal, a network terminal, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention.

In the several embodiments provided by the present invention, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or can be integrated into another system, or some features can be ignored, or not implemented. On the other hand, the coupling or direct coupling or communication connection between each other shown or discussed may be through some interfaces, and the indirect coupling or communication connection of the devices or units may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or they may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit.

What is disclosed above is only the preferred embodiment of the present invention, but the present invention is not limited thereto. Any non-creative changes that those skilled in the art can think of, as well as several improvements and modifications made without departing from the principles of the present invention can be made. , should all fall within the protection scope of the present invention.

Claims (10)

1. A small signal equivalent modeling method for direct drive wind farms, which is characterized by including the following steps: Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine; The wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine equivalent impedance model. The wind turbine equivalent impedance model is a function of circuit parameters and control parameters; Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the dominant factor parameter of the current frequency band; For each frequency band, the dominant factor parameters of the current frequency band are identified to correct the errors caused by the aggregation approximation calculation; By aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, the final wind turbine equivalent impedance model is obtained. 2. The small-signal equivalent modeling method of a direct-drive wind farm according to claim 1, characterized in that the wind turbine equivalent impedance model is obtained by performing an aggregated approximate calculation on the wind turbine impedance of the expanded wind turbine, which specifically includes: (a) Ignore the influence of the collector line, treat multiple wind turbines in the same branch as a purely parallel relationship, and consider that the operating points, circuit parameters and control parameters of the wind turbines in the same branch are the same, and the impedance of each wind turbine is the same , assuming that there are N wind turbines directly connected in parallel on the branch, the aggregate impedance of the wind turbines is expressed as: (1) Among them, Z _g is the filter impedance, Z _gsc is the grid side converter impedance, Z _ig and Z _ug are the phase locked loop impedances, and E is the unit matrix; (b) According to the principle of parallel connection, the quantitative relationship between the impedances of each part of the fan unit before and after equal value is obtained. The formula is expressed as: (2). 3. The small signal equivalent modeling method of direct drive wind farm according to claim 2, characterized in that the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter is calculated in the entire frequency band, and the entire frequency band is divided into For multiple frequency bands, select at least one parameter with the highest sensitivity in each frequency band as the dominant factor parameter of the current frequency band, including: (a) Define the control parameters and circuit parameter set of the wind turbine, expressed as: x _{WT_para} ={ x ₁ , x ₂ , _… , x _D } (3) Among them, D represents the number of parameters; (b) In the full frequency range [H1, H2] Hertz, the sensitivity is calculated for all parameters every h Hertz step. The sensitivity K _s calculation formula is expressed as: K _si = (4) K _si represents the sensitivity of the i-th parameter; (c) Divide the entire frequency band into M frequency bands, calculate the average sensitivity of each parameter in each frequency band, and select at least one parameter with the largest average sensitivity in each frequency band as the dominant factor parameter of the current frequency band. 4. The small signal equivalent modeling method of direct drive wind farm according to claim 3, characterized in that, for each frequency band, the dominant factor parameters of the current frequency band are identified to correct the error caused by the aggregation approximate calculation, specifically including : For each frequency band, the particle swarm algorithm is used to identify the dominant factor parameters of the current frequency band. The fitness function of the particle swarm algorithm is: (5) Among them, Z _br represents the detailed impedance of the equivalent front branch of the wind turbine, and Z _br ^eq represents the equivalent impedance of the branch; s is the frequency domain operator, s _{m, min} , s _{m, max} represent the boundary point of the m-th frequency band interval, is the j-th dominant factor parameter of the m-th frequency band. 5. The small-signal equivalent modeling method of direct drive wind farm according to claim 4, characterized in that the final wind turbine equivalent is obtained by aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results. Impedance model, specifically including: Through formula (1) and formula (5), the final wind turbine equivalent impedance model is obtained, and the expression is: (7) Among them, d represents the d-axis component in the dq coordinate system, and q represents the q-axis component in the dq coordinate system. 6. The method for small-signal equivalent modeling of direct-drive wind farms according to claim 5, characterized in that when performing an aggregated approximate calculation on the wind turbine impedance of the expanded wind turbine to obtain the equivalent impedance model of the wind turbine, the following steps are also included: : Perform an aggregate approximate calculation on the collector line impedance of the expanded wind turbine to obtain the collector line equivalent impedance model; The transformer equivalent impedance model is obtained by aggregate approximate calculation of the transformer impedance of the expanded wind turbine. 7. The small-signal equivalent modeling method of a direct-drive wind farm according to claim 6, characterized in that an aggregated approximate calculation is performed on the collector line impedance of the expanded wind turbine to obtain a collector line equivalent impedance model, which specifically includes: The constant power loss method is used for equivalence. It is considered that the power loss on the collector line before and after equivalence is inconvenient. The collector line is equivalent to an aggregate impedance. Then the expression of the collector line equivalent impedance model is: (8) Among them, Z _Li is the line impedance of the i-th unit branch; P _Li is the loss flowing through the impedance Z _Li ; Perform an aggregated approximate calculation on the transformer impedance of the expanded wind turbine to obtain the transformer equivalent impedance model, which includes: If the end transformer of a wind turbine is equivalent to an expansion transformer located at the end of an equivalent wind turbine, and the impedance of the expansion transformer is the parallel connection of the impedances of all wind turbine end transformers, then the calculation formula for the equivalent capacity and equivalent impedance of the expansion transformer is expressed for: (9) Among them, S _{T_eq} and Z _{T_eq} are the equivalent capacity and equivalent impedance of the expansion transformer respectively, and S _Ti and Z _Ti are the capacity and impedance of _{the i} -th wind turbine unit end transformer in the original wind farm. 8. A direct-drive wind farm small-signal equivalent modeling system, characterized by: Equivalent impedance model aggregation calculation module: Using the multi-machine equivalent modeling principle, the wind turbines on each branch are equivalent to an expanded wind turbine; the wind turbine impedance of the expanded wind turbine is aggregated and approximated to obtain the wind turbine, etc. Value impedance model, the wind turbine equivalent impedance model is a function of circuit parameters and control parameters; Dominant factor parameter selection module: Calculate the sensitivity of the detailed impedance of the equivalent front branch of the wind turbine to each parameter in the entire frequency band, divide the entire frequency band into multiple frequency bands, and select at least one parameter with the highest sensitivity in each frequency band as the current The dominant factor parameters of the frequency band; Dominant factor parameter identification module: For each frequency band, identify the dominant factor parameters of the current frequency band to correct the error caused by the aggregation approximation calculation; Equivalent impedance model correction module: By aggregating the approximately calculated wind turbine equivalent impedance model and the dominant factor parameter identification results, the final wind turbine equivalent impedance model is obtained. 9. A terminal, characterized in that it includes: Memory used to store small signal equivalent modeling programs for direct drive wind farms; A processor, configured to implement the steps of the direct-drive wind farm small signal equivalent modeling method according to any one of claims 1 to 7 when executing the direct-drive wind farm small signal equivalent modeling program. 10. A computer-readable storage medium, characterized in that a direct-drive wind farm small signal equivalent modeling program is stored on the readable storage medium, and the direct-drive wind farm small signal equivalent modeling program is processed When the device is executed, the steps of the direct drive wind farm small signal equivalent modeling method as described in any one of claims 1 to 7 are realized.